Water-soluble resins and their preparation, said resins resulting from simultaneous condensation of a ketone, an aldehyde, a monohydric phenol and resorcinol



United States Patent 0 3,412,068 WATER-SOLUBLE RESINS AND THEIR PREPARA-TION, SAID RESINS RESULTING FROM SIMUL- TANEOUS CONDENSATION OF AKETONE, AN ALDEHYDE, A MONOHYDRIC PHENOL AND RESORCINOL Robert M.Gemrnill, Jr., Woodbury, and John W. Schick, Cherry Hill, N.J.,assignors to Mobil Oil Corporation, a corporation of New York NoDrawing. Continuation of application Ser. No. 369,008, May 20, 1964.This application Sept. 28, 1967, Ser. No. 671,485

8 Claims. (Cl. 26050) ABSTRACT OF THE DISCLOSURE An improvedwater-soluble, thermosettable resin is produced by reacting an aldehyde,a ketone,'and a phenol in a one-step polycondensation reaction that iscatalyzed with a base, in which 1-25 mole percent of the phenol isrecorcinol. In the final resin product, the molar proportions ofaldehyde, ketone, and phenol present are between about 3 and about 6moles of the aldehyde, between about 1 and about 1.5 moles of the ketoneper mole of the phenol. These resins are useful as binders for bondedproducts made from fibers, particles, or sheets, which bonded productspossess properties of high bond strength and are resistant againstweakening of the bond from exposure to water. The use of resorcinolprovides resins having improved solubility and longer shelf life.Resorcinol is the only polyhydroxy phenol found to give suchimprovement.

This application is a continuation of application Ser. No. 369,008,filed May 20, 1964, now abandoned.

This invention relates to improved water-soluble resins, and moreparticularly improved water-soluble ketone-aldehyde-phenol resins, whichcan be thermoset to provide binders for fibers, particles and sheets.The invention also relates to a process for making such resins, and tobonded products containing a binder produced by thermosetting suchresins.

As is well known to those familiar with the art, a wide variety ofconstruction boards have been produced by bonding fibers, particles, andsheets with suitable binders. Such boards include plywood, chip board,particle board, fiberboard, laminates and others. In this specificationand the claims, the terms fibers, particles, and sheets encompass a widevariety of materials of mineral and vegetable origin, and syntheticorganic materials like Dacron and nylon. Typical minerals from which construction materials can be made include gypsum, asbestos, fiberglass andthe like. However, construction boards which are more economical formany purposes can be made by bonding fibers, particles or sheets ofvegetable origin, usually cellulosic materials into desiredconfigurations. The term cellulosic, as used herein, is embracive ofsubstances from various plants and trees that contain thelignocellulosic complex. The term cellulosic materials, therefore, asused herein includes fibers, chips, shavings, sheets, sawdust and thelike derived from various plants and trees, and also includes hardwoods, soft woods, cotton, bagasse, kenaf, hemp and jute.

A variety of materials have been proposed for use as binders for fibers,particles and sheets. Materials that can be thermoset to provide aninfusible binder lending greater strength and durability to the bondedproducts are highly desirable. Phenol-formaldehyde, urea-formaldehydeand melamine-formaldehyde resins are among the numerous thermosettablematerials that have been proposed for such uses.

3,412,068 Patented Nov. 19, 1968 However, products bonded with varioustypes of previously-used thermosettable materials have often been foundto lose bond strength more rapidly when exposed to the elements thanwhen protected from the weather, as a result of gradual deterioration ofthe binders from frequent or prolonged contact with water. Accordingly,resins which can be thermoset to provide a binder which retains itsstrength despite exposure to weather or to water from other sources areespecially desirable for Ohtaining bonds which are more durable inadverse environments, and particularly under severe weather conditions.

In addition to being thermosettable to provide bonds having highstrength and good resistance to loss of strength from contact withwater, the resins must be characterized by properties which facilitatetheir use as binder materials. Before being thermoset, the resins aremost conveniently dissolved in a solvent for application to the fibers,particles or sheets as a solution or a pastelike slurry. To avoid thesafety hazards associated with the use of organic solvents, especiallyat elevated temperatures, thermosettable resins which are water-solubleare highly desirable. Further, it is highly desirable that the resin bewater-soluble throughout a broad range of concentrations so that it canbe transported in solutions of relatively high concentrations or appliedin any of various concentrations most convenient for the particularthermosetting process. Additionally, it is desirable that the resinsolutions have good shelf life, i.e., that they do not become lesswater-soluble and precipitate from solution during intervals of storageor transport.

However, most thermosettable resins used in the past have exhibitedsignificant water-solubility only in conjunction with relatively lowmolecular weights and correspondingly low viscosities. During thethermosetting process, which employs elevated temperatures andpressures, resins of low viscosity tend to penetrate the material beingbonded, often leaving insucient binder at the bonding points andresulting in an unacceptably weak bond. Specifically, ketone-aldehyderesins having a molar ratio of between one and two moles of aldehyde permole of ketone have had sufiicient viscosity for acceptable bond only inwater-insoluble forms requiring the use of an organic solvent such as analcohol or an ester. It has been proposed that resins which are morewater-soluble might be produced by the reaction of between 3 and 5 molesof aldehyde with each mole of ketone, but the resins so produced do notcure to give satisfactory 'bond strength. To the best of our knowledge,ketone-aldehyde resins used in the past are completely or largelywater-insoluble, requiring the addition of an organic solvent beforeapplication to the materials to be bonded, or they have not providedsatisfactory bond strength on being thermoset.

It has also been proposed that incorporation of a phenolic compound inthe resin might enhance its curing characteristics and bond strengthbut, to the best of our knowledge and with the exception of the resindisclosed in copending application for Letters Patent, Ser. No. 354,435,filed Mar. 24, 1964, by Robert M. Gemmill, Jr., John W. Schick and JohnH. Stockinger, the ketonealdehyde-phenol resins used in the past havealso been water-insoluble or only poorly water soluble, againnecessitating the use of an organic solvent for convenient applicationof the resin to the materials to be bonded.

As disclosed in the aforementioned copending Application Ser. No.354,435, resins which are highly watersoluble, even in solutions whichare substantially neutral, e.g. having a pH of between 7.0 and 9.0, andwhich can be thermoset to provide bonds which retain good strength, evenunder exposure to water or severe weather conditions, can be produced bythe reaction of controlled proportions of a ketone reactant, an aldehydereactant and a phenol reactant in the presence of a basic catalyst.

It has now been found that improved resins which are highlywater-soluble throughout even greater ranges of resin concentrations,even in substantially neutral solutions and for extended periods oftime, and which have viscosities and other characteristics suitable forbeing thermoset to provide bonds which retain good strength, even underadverse weather conditions or other exposure to water, can be producedby the reaction of controlled proportions of a ketone, an aldehyde, amonohydroxy phenolic compound and resorcinol in the presence of a basiccatalyst.

Accordingly, it is a broad object of this invention to provide animproved binder for fibers, particles and sheets. Another object is toprovided bonded products bonded with the improved binder. Another objectis to provide an improved water-soluble resin of desirably highviscosity, which can be thermoset to provide such an improved binder. Aspecific object is to provide a resin of improved water-solubilitythroughout a range of resin concentrations, which can be thermoset toprovide a binder for cellulosic materials and which can be prepared byreaction of a ketone, an aldehyde, a monohydroxy phenolic compound andresorcinol. Another specific object is to provide bonded productscomprising cellulosic materials and a binder produced by thermosettingsuch a resin, and having high bond strength and good resistance to bondstrength deterioration from exposure to water and adverse weatherconditions. Other objects and advantages of this invention will becomeapparent to those skilled in the art, from the following detaileddescription.

In general, the present invention provides an improved water-solubleresin which can be thermoset to provide a binder for bonded productsmade from fibers, particles or sheets, which bonded products haveproperties of high bond strength and resistance against weakening of thebond from exposure to water. The improved watersoluble resin of thisinvention comprises the product of the reaction of an aldehyde, a ketoneand at least two phenolic compounds in molar proportions of betweenabout 2 and about 8 moles of aldehyde per mole of the phenolic compoundsand of between about 0.5 and about 2 moles of ketone per mole of thephenolic compounds, and in the presence of a base capable of catalyzingthe condensation reaction of the aldehyde, the ketone and the phenoliccompounds, said phenolic compounds comprising a monohydroxy phenoliccompound and resorcinol, and said resorcinol constituting between aboutone mole percent and about 25 mole percent of said phenolic compounds.

The foregoing molar proportions of aldehyde, ketone and phenoliccompounds in the resin of this invention can be alternatively expressedon the basis of a mole of the ketone. So expressed, the aldehyde, ketoneand phenolic compounds are present in the resin in molar proportions ofbetween about 1 and about 16 moles of aldehyde per mole of ketone andbetween about 0.5 and about 2 moles of phenolic compounds per mole ofketone, said phenolic compounds comprising a monohydroxy phenoliccompound and resorcinol, and said resorcinol constituting between aboutone mole percent and about 25 mole percent of said phenolic compounds.

The invention also includes the process of making such resin, whichprocess comprises reacting an aldehyde, a ketone and at least twophenolic compounds in'molar proportions of between about 2 and about 8moles of aldehyde per mole of the phenolic compounds and of betweenabout 0.5 and about 2 moles of ketone per mole of the phenoliccompounds, and in the presence of a base capable of catalyzing thecondensation reaction of the aldehyde, the ketone and the phenoliccompounds, said phenolic compounds comprising a monohydroxy phenoliccompound and resorcinol, and said resorcinol constituting between aboutone mole percent and about 25 mole percent of said phenolic compounds.

7 The invention also provides a bonded product, e.g. one comprisingcellulosic material, bonded with a binder produced by thermosetting thewater-soluble resin of this invention.

The ketone reactant used in the preparation of the resin of thisinvention can be any ketone having at least one hydrogen atom on eachcarbon atom alpha to the carbonyl group, or a mixture of two or more ofsuch ketones. Suitable ketones include the aliphatic, particularly loweralkyl, and the cycloaliphatic ketones. Non-limiting examples of theketone reactant are acetone, methyl ethyl ketone, ethyl ketone, methylpropyl ketones, methyl butyl ketones, ethyl propyl ketones, dihexylketone, cyclohexanone, acetonyl acetone, diacetone, and mixtures of anyof the foregoing ketones. Preferred ketone reactants are acetone, methylethyl ketone and other ketones having alkyl groups containing up tothree carbon atoms attached to the carbonyl group, with acetone beingparticularly preferred.

. The aldehyde reactant used in the preparation of the resin of thisinvention can be any compound having an active group characteristic ofthe aldehydes. Suitable aldehyde reactants include the aliphaticaldehydes and aromatic aldehydes, including heterocyclic aldehydes.Non-limiting examples of suitable aldehyde reactants are formaldehyde(including polymeric forms, e.g. paraformaldehyde) acetaldehyde,propionaldehyde, butyraldehyde, acrolein, crotonaldehyde, tiglaldehyde,benzaldehyde, salicylaldehyde, cinnamaldehyde, glyoxal and mixtures ofany of the foregoing aldehydes. Formaldehyde, being inexpensive andreadily available, is a preferred aldehyde reactant. One of the twophenolic compounds required for preparation of the resin of thisinvention is monohydroxy phenolic compound which can be any monohydroxyphenol charactertized by having one hydroxy group attached to itsnuclear ring and hydrogen atoms in at least two and preferably at leastthree active nuclear positions. Particularly suitable monohydroxyphenolics include unsubstituted phenol and substituted phenols such asalkyl phenols in which the alkyl groups are preferably lower alkylgroups, e.g. cresols. Other preferred types of substituted monohydroxyphenolics include meta-substituted phenols and various para-substitutedphenols, e.g. p-amino phenol. Non-limiting examples of monohydroxyphenolics suitable for use in the reaction of this invention includephenol, cresols, xylenols, ethylphenols, propylphenols, butylphenols,amylphenos, phenyphenols, cyclohexylphenols and mixtures of any of theforegoing phenols. Mononuclear phenols of lower molecular weight arepreferred, as are phenols which Iare relatively unemcumbered againstring reactions, such as, if a substituted monodydroxy phenolic reactantis desired, a phenol which is substituted by relatively few groups.

The other of the two phenolic compounds required for preparation of theresin of this invention is resorcinol (1,3-diyhdroxybenzene). It is animportant aspect of this invention that the inclusion in the resin ofbetween about one mole percent and about 25 mole percent of resorcinol,based on total phenolic compounds in the resin, is productive of a resinhaving a higher viscosity and having a high degree of water-solubilityover greater ranges of resin concentration in the aqueous solutions,particularly in the lower ranges of resin concentrations. In general,and depending on the specific aldehyde, ketone and monohydroxy phenolicreactants used and the specific process conditions employed, an increasein the mole percentage of resorcinol included in the resin isaccompanied by a reduction in the minimum resin concentration at whichthe resin is substantially completely water-soluble. With the particularketone, aldehyde and monohydroxy phenolic reactants used in the specificexamples described hereinafter, it was found that increases in the molepercentage of resorcinol in the resin between about one and about 8-10mole percent, based on total phenolic compounds in the resin, wereaccompanied by increases in the maximum amount of water with which theresin could be diluted without diminishment of the substantiallycomplete solubility of the resin in the aqueous solution, in some casesto an infinite amount of water; with further increases in the resorcinolcontent in the resin, between about 8-10 and about mole percent, themaximum amount of water with which the resin could be diluted withoutdiminishing its substantially complete solubility therein remainedstable near the maximum corresponding to 8-10 mole percent resorcinol.

In the synthesis of the resin of this invention, the purity of theketone, aldehyde and phenolic compounds in the reaction mixture is notcritical, so long as there are the proper mole ratios of reactants inthe mixture. Accordingly, the reactants need not be combined in theirpure forms, but one or more of them may instead be added to the mixturein an impure form, such as in a form including side products resultingfrom the reaction or decomposition of other compounds to fonm theketone, aldehyde, monohydroxy phenol or resorcinol. For example, theketone and monohydroxy phenolic compound can be added to the reactionmixture in the form of the unpurified product of the decomposition of anaryldialkyl methylhydroperoxide. By way of illustration, when thedesired ketone reactant is acetone and the desired monohydroxy phenolicreactant is unsubstituted phenol, cumene hydroperoxide can beconveniently decomposed under anyhdrous conditions to yield a cumenesolution of acetone and phenol, which solution can be used in theprocess of this invention without purification or removal ofdecomposition by-products such as minor proportions of acetophenone andalpha-methyl styrene, and without impairment of the water-solubility ofthe resin produced or of the strength or Water-resistance of the bondproduced by thermosetting the resin. In general, ketone and phenolicreactants can be derived for use in the process of this invention by thedecomposition of any aryldialkyl methylhydroperoxide having the FormulaI:

wherein R is alkyl and preferably lower alkyl (C -C R is alkyl orhydrogen and R" is alkyl, hydrogen or dialkyl methylhydroperoxide. Theselection of a specific aryldialkyl methylhydroperoxide will depend onthe nature and ratio of specific ketone and phenolic reactants desiredfor use in the resin-productive reaction. Nonlimiting examples ofaryldialkyl methylhydroperoxides suitable for this purpose includecumene methylhydroperoxide, dirnethyl cumene hydroperoxide, methyl ethylcumene hydroperoxide and diethyl cumene hydroperoxide. Since acetone isa preferred ketone and (unsubstituted) phenol a preferred phenol forpurposes of this invention, cumene hydroperoxide is preferred as anaryldialkyl methylhydroperoxide which can be quantitatively decomposedto; yield acetone and phenol. Similarly, a ketone reactant landresorcinol can be derived for use in the process of this invention bythe decomposition of any aryldialkyl methlyhdroperoxide having theaforeshown Formula I, wherein R is alkyl and preferably lower alkyl (C-C R is alkyl or hydrogen, and R is a dialkyl methylhydroperoxide groupin a ring position which is meta with respect to the other dialkylmethylhydroperoxide on the ring.

The reaction productive of the water soluble resins of this invention isa condensation reaction which is basecatalyzed. The catalyst can be anybase which is capable of catalyzing the reaction of the ketone reactant,the aldehyde reactant, the monohydroxy phenolic reactant and resorcinol.The catalyst will generally be added in a catalytic amount tothereaction mixture in the form of an aqueous solution, e.g. an aqueoussolution having a concentration of between 1% and 20% of a stronglyionized base, such as sodium hydroxide or potassium hydroxide, or as aconcentrated solution of a partially ionized base such as ammoniumhydroxide, although the concentration of the base as added to thereaction mixture is not critical. In general practice, when a stronglyionized base is used, it will preferably be present in the reactionmixture in a concentration between 0.02 mole and 0.15 mole, and morepreferably between 0.05 mole and 0.08 mole, of the base per mole ofphenolic compounds initially present in the reaction mixture. When apartially ionized base is used, it will preferably be present in thereaction mixture in a concentration between 0.03 mole and 0.08 mole, andmore preferably about 0.07 mole, per mole of phenolic compoundsinitially present in the reaction mixture.

It has been found that the ketone-aldehyde-monohydroxyphenol-resorcinolresin of this invention, which is water-soluble throughout a broad rangeof resin concentrations in aqueous solutions and which can be thermosetto effect a bond having good strength and high resistance againstweakening of the bond by exposure to Water or severe weather conditions,can be produced by controlling the proportions of ketone, aldehyde,monohydroxy phenol and resorcinol initially present in the reactionmixture from which the resin is condensed, and thereby controlling theproportions of ketone, aldehyde, monohydroxy phenol and resorcinol whichcondense to form the resin. The resin of this invention, which isbelieved to be a ketonealdehyde-monohydroxy phenol-resorcinol copolymer,is the product obtained, as stated hereinbefore, by reacting a ketone,an aldehyde and at least two phenolic compounds in molar proportions ofbetween about 2 and about 8 moles, preferably between 3 and 6 moles, ofaldehyde per mole of the phenolic compounds and of between about 0.5 andabout 2 moles, preferably between 1.0 and 1.5 moles, of ketone per moleof the phenolic compounds, said phenolic compounds comprising amonohydroxy phenolic compound and resorcinol, and said resorcinolconstituting between about 1 mole percent and about 25 mole percent ofsaid phenolic compounds.

It has been found that this resin can be obtained by reacting a ketone,an aldehyde, a monohydroxy phenol and resorcinol in the presence of abase capable of catalyzing reaction of the ketone, the aldehyde, themonohydroxy phenol and resorcinol, and in the presence of an excess ofthe ketone of between 50% and over that proportion of said ketone whichis reacted to form the aforedescribed ketone-aldehyde-monohydroxyphenolresorcinol resin of this invention. With such an excess of ketonepresent, the ratios of aldehyde, ketone, and phenolic compoundsinitially present in the reaction mixture are between about 2 and about8 moles of aldehyde per mole of the phenolic compounds and between about0.7 and about 4 moles of ketone per mole of the phenolic compounds, saidphenolic compounds comprising a monohydroxy phenolic compound andresorcinol, and said resorcinol constituting between about 1 molepercent and about 25 mole percent of said phenolic compounds. Theimmediately preceding molar ratios of ketone, aldehyde and phenoliccompounds initially present in the reaction mixture can be alternativelyexpressed on the basis of a mole of ketone. So expressed, the ratios ofketone, aldehyde and phenolic compounds initially present in thereaction mixture are between about 0.5 and about 11 moles of aldehydeper mole of ketone and between about 0.2 and about 1.4 moles of thephenolic compounds per mole of ketone, said phenolic compoundscomprising a monohydroxy phenolic compound and resorcinol, and saidresorcinol constituting between about one mole percent and about 25 molepercent of said phenolic compounds.

The condensation reaction involved in this invention can be carried outin the presence of water, which can be introduced by adding the basiccatalyst in aqueous solution or by charging at least a part of thealdehyde reactant in an aqueous solution, such as formalin whenformaldehyde is the aldehyde reactant. The total amount of water used isnot a critical factor, except that there should be sufficient waterpresent to dissolve the resin product. There can be as much as 30 molesor more of water per mole of the phenolic compounds present in thereaction mixture, with the maximum amount of water used usually beinglimited only by the amount that can be handled, as a practical matter.After reaction, the water content of the resin solution can be adjustedas described hereinafter.

The reaction between the ketone, the aldehyde, the monohydroxy phenoliccompound and resorcinol will generally be carried out at temperaturesbetween about 125 F. and about 350 F. Within such a range oftemperatures, the process is generally carried out at relatively highertemperatures when using a relatively less ionized base as the reactioncatalyst, and at relatively lower temperatures when using a relativelymore ionized base as reaction catalyst. In preferred practice, when astrongly ionized base, e.g. sodium hydroxide, is used as catalyst, thereaction will preferably be carried out at temperatures between 125 F.and 195 F., while the reaction will preferably be conducted attemperatures between 225 F. and 300 F. when the catalyst is a base whichis only partially ionized, e.g. ammonium hydroxide. Within the aforesaidtemperature ranges, a decrease in the strength of the base can generallybe compensated by an increase in the reaction temperature. The reactiontime required to produce the water-soluble resin of this invention willvary inversely with the reaction temperature and will he usually betweenminutes and 4 hours, and more frequently between 30 minutes and 3 hours.When it is desirable to conduct the reaction at a slightly lowertemperature for a slightly longer period of time, this can beaccomplished by any suitable method of controlling the temperature ofthe reaction mixture, such as by removing heat of reaction from thereaction vessel by heat exchange, e.g. with a water-filled coolingjacket, or by controlling the rate of addition of the basic catalyst tothe reaction mixture, e.g. by adding the catalyst continuously or intime-spaced increments rather than adding all of the catalyst to themixture before reaction has begun.

It will be recognized that, at the reaction temperatures used, some orall of the catalyst, water, and many aldehyde and ketone reactants, willbe volatile. Accordingly, in order to obtain good yields of thewater-soluble resins of this invention, some provision should be made toretain the reactants in the reaction vessel. This can be done by using arefiux condenser. Preferably and more feasibly, the reaction can becarried out in an enclosed vessel, such as a kettle or an autoclave. Inthis case there will be a pressure build-up attributable to thevaporization of reactants.

Upon completion of the reaction, the resin product is present in a. moreor less viscous, aqueous solution. The basic catalyst can be destroyedby neutralization with an acid, such as hydrochloric acid or carbondioxide. Following neutralization of the catalyst, the resinconcentration in the solution can be adjusted, by adding or removingwater, to any of the various levels desired for various commercial usesof the resin. The resin of this invention can be dissolved inconcentrations as high as 65 wt. percent or more, which are desirablefor thermosetting uses in which more dilute resin solutions mightexcessively penetrate the porous bonded surfaces and result in what isknown as a starved glue line characterized by unacceptably low bondstrength. To obtain such highly concentrated solutions, the removal ofwater is feasibly effected by heating the resin solution under reducedpressure. It has also been found that by the use of carefully controlledratios of various forms of the aldehyde reactant and by carefullycontrolling the amount of water charged, it is possible to producemixtures which, following reaction, contain as high as wt. percentresin. For example, when formaldehyde is used as the aldehyde reactant,it can be introduced into the reaction mixture as a controlled ratio offormalin solution (37% formaldehyde) and paraformaldehyde, or as acontrolled ratio of solid paraformaldehyde and water, to obtain amixture which, following reaction, will contain about 65 wt. percentresin without further adjustment of the water content. Particularly incases in which water resistance of the binder is not the most importantof desired properties, the resin can be applied in this form for use asa thermoplastic binder for particles, fibers, sheets or other materials.

On the other hand, it is an important advantage of the resin of thisinvention that it is substantially completely water-soluble inrelatively low concentrations, particularly in concentrations as low as30 wt. percent and lower, which are appropriate for other commercialuses of the resin in which it is desirable to use a relatively diluteresin solution. It is another important advantage of the resin of thisinvention that it has a viscosity which is both low enough to facilitateits use in spray applications of aqueous solutions having a resinconcentration as high as 65 wt. percent or higher, and high enough thatit can be applied for thermosetting purposes in aqueous solutions havinglower resin concentrations, e.g. between 30 wt. percent and 60 wt.percent or even lower, without excessive resin penetration of the poroussurfaces to be bonded.

To produce bonded products having strong bonds and good resistanceagainst weakening of the bonds from exposure to water, the water-solubleresin of this invention can be thermoset to form an insoluble, infusiblepolymer with the use of a basic catalyst. A mixture of a basic catalystand a water solution of the resin, having proper viscosity, is appliedto fibers, particles or sheets, and bonded products are formed therefromby molding under heat and pressure to cure the resin to a thermosetpolymeric binder. To form bonds of strength equivalent to or greaterthan that regarded in the industry as acceptable for conventional uses,the water-soluble resin of this invention should be applied, priod tobeing thermoset, in an aqueous solution having a proper resinconcentration, e.g. between 30% and 65% or higher, and having aviscosity between about 5 seconds and about 9 seconds at between 62% and65 resin content when measured by the Gardner-Holt method (ASTMDesignation D154560) at ambient temperature (about 77 F.).

In cases where the reacted mixture containing the resin has the properviscosity to be applied without water content adjustment, thecondensation reaction catalyst present in the reacted mixture maysuffice as the thermosetting catalyst, so that the addition of morecatalyst would not be necessary. Otherwise, the basic catalyst used inthe curing (thermosetting) step can be sodium carbonate or an inorganicbase such as ammonium hydroxide or alkali or alkaline earth metalhydroxides (e.g. sodium hydroxide, potassium hydroxide, or calciumhydroxide), or an organic base such as a dialkylamine (e.g.dimethylamine or diethylamine), an alkylenediamine (e.g.ethylenediamine), a polyalkyleneamine (e.g., hexamethylenetetramine,diethylenetriarnine or triethylenediamine), an alkyleneimine (e.g.pyrroline, pyrrolidine, piperidone or piperazine), an amine-terminatedpolyamide resin, or guanidine. The amount of basic catalyst used toeffect the thermosetting cure is generally between about 0.5 percent andabout 12 percent, by weight of the resin. Generally, about 2 to 8percent is satisfactory.

As has been mentioned hereinbefore, the bonded products of thisinvention include particle board, fiber board and plywood. They are allprepared by the same general ethod of covering a surface of the fibers,particles or sheets with the binder, and the heating under pressure.

Particle board can be prepared from various particles manufactured forthis use, or it can include wood particles found as waste in sawmills,lumber yards, carpentry shops, etc. Such waste particles can includesawdust, chips, or shavings. Waste ends can also be used, if they arecomminuted to a proper particulate form. Wood particles coated with thebinder and thermosetting catalyst are generally placed in a moldingpress of desired size and shape and subjected to heat and pressure. Thecompactness and hardness of the product particle board is governed to agreat extent by the amount of pressure used. In general, pressures offrom about 50 *p.s.i.g. up to about 800 p.s;i.g. are employed. Moldingisusually carried out at temperatures between about 300 F. and about 425F. The molding temperature should not exceed temperatures in the orderof about 450 F., above which charring of the cellulosic material mayoccur. The preferred molding time will be dependent upon the temperatureand flow characteristics of the resin being thermoset. Time should beallowed to permit the resin to be distributed evenly and to thermosetsufficiently to provide a board of reasonable uniformity. The period oftime can be between about 3 minutes and about 1 hour. In generalpractice, molding time will generally be between about 3 minutes andabout 15 minutes.

Fiberboards are prepared by admixing mineral or vegetable fibers withthe resin of this invention and catalyst. The resin of this invention isparticularly advantageous for making fiberboards from relativelyinexpensive or Waste fibers, such as kenaf and bagasse. The mixture .offibers and binder is then molded into boards, using the techniquesdescribed for particle boards.

Plywoods are made by coating the surfaces of thin sheets of wood withmixtures of the resin and catalyst for thermosetting the resin. Thecoated wood sheets are then stacked one on top of another to the desiredthickness, usually with the directions of the grain of adjacent sheetsoriented at right angles to each other. The stack of sheets or plys isthen heated under pressure, usually applied at right angles to theresin-coated surfaces.

If it is desirable to extend the resin of this invention, e.g. foreconomic reasons, this can be accomplished by adding a filler to theresin prior to the thermosetting step. Fillers which are suitable forthis purpose, such as for example, clay, wood flour, soya flour, anddried blood, can be added in relatively large proportions withoutinrpairing the properties of good bond strength and resistance to bondweakening from the action of water which are characteristic of thebinder obtained by thermosetting the resin of this invention.

The amount of resin applied to the cellulosic material to make theparticle boards, fiberboards or plywood board should be sufficient thatthe finished board will contain, by weight, between about 4% and about30% of binder.

The following specific examples are for the purpose of illustrating thepreparation of the resin of this invention from a ketone, an aldehyde, amonohydroxy phenolic compound and resorcinol, and further demonstratethe effect of variables upon bond strength of the thermoset binderproduced with the resins. It will be understood that this invention isnot to be limited to the specific reactants and catalysts used in theexamples, or to the particular operations and manipulations involved.Other ketone, aldehyde and monohydroxy phenolic reactants and catalystas defined hereinbefore can be used, as those skilled in the art willreadily appreciate.

Example I A reaction mixture containing 116.0 grams (2 moles) ofacetone, 90.0 grams of paraformaldehyde (3 moles of formaldehyde), 84.6grams (0.9 mole) of phenol, 11.0 grams (0.1 mole) of resorcinol and 180grams of water was heated to 140 F. with rapid stirring. 25 millilitersof aqueous sodium hydroxide was continuously added over a period of 30minutes, and the reaction mixture was then refluxed for 2.5 hours at 185F. The product was stripped of all unreacted acetone and of sufiicientwater to raise the concentration of the aqueous solution to 59% resinsolids. The viscosity of the 59% resin solution ranged from 1.5 to 3seconds on the Gardner-Holt scale. It was found that the 59%' resinsolution could be diluted with additional water, in any volume up to aninfinite amount, without decreasing the solubility of the resin content,i.e., without resulting in precipitation of any of the resin contentfrom the aqueous solution. In a second run identical to the first run ofthis example except that an additional 9.4 grams (0.1 mole) of phenolwas substituted for the 0.1 mole of resorciriol, an aqueous solutioncontaining 59% resin product had a Gardner- Holt viscosity of 1.2seconds. The maximum volume of additional water with which the 59%resinsolution could be diluted without causing precipitation of resincontent was 1.45 times the volume of the 59% resin solution.

Data demonstrating lap shear strength of bonds obtained by thermosettingthe resins productd in Runs 1 and 2 of this example are given in TableI.

Example II A reaction mixture containing 116.0 grams 2 moles) ofacetone, 90.0 grams of paraformaldehyde (3 moles of formaldehyde), 56.4grams (0.6 mole) ofphenol, 32.4 grams (0.3 mole) of m-cresol, 11.0 grams(0.1 mole) of resorcinol and grams of Water was heated to 140 F. withrapid stirring. 25 milliliters of 10% aqueous sodium hydroxide wascontinuously added over a period of 20 minutes, and the reaction mixturewas then refluxed for 2.7 hours at F. The product was stripped of allunreacted acetone and of sufiicient' water to raise the concentration ofthe aqueous solution .to 62% resin solids. The viscosity of the 62%resin solution ranged from 5 to 13.2 seconds on the Gardner-Holt scale.It was found that the 62% resin solution could be diluted withadditional water, in any volume up to an infinite amount, withoutimpairing the solubility of the resin content, i.e., without causingprecipitation of resin content from the aqueous solution. 1.

In a second run identical to the first rpn of this example except thatan additional 6.3 gram (0.067 mole) of phenol and 3.6 grams (0.033 mole)0f;.m-cresol were substituted for the 0.1 mole of resorcinol, an aqueoussolution containing 60% resin had a Gardner-Holt viscosity ranging from2.5 to 4.3 seconds. The maximum volume of water with which the 60% resinsolution could be diluted, without causing precipitation of resincontent, was equal to the volume of the 60% resin solution.

Data demonstrating lap shear strength of bonds obtained by thermosettingthe resins produced in Runs 1 and 2 of this example are given in TableI.

Shear stress tests were performed to determine the bonding strength ofeach of the binders produced by thermosetting, in the manner describedhereinbefore, each of the resins produced aS described in Examples I andII. Prior to the bond strength tests, 8 percent diethylenetriaminecatalyst, based upon the weight of the resin, was admixed with the resinunder test. The mixture of resin and catalyst was then used to coat onesquare inch of lapped birch veneers. The resins were cured at 350 F. for10 minutes, at just sufficient pressure to hold the veneers together.Medical tongue depressors /2 by 6") were used as the birch veneers. Thelapped samples were conditioned for 48 hours at 70 F. and 50% relativehumidity. Thereafter, the stress required to pull the lapped sectionapart by shearing was determined on a Tinius Olsen Stress instrument andnoted in Table Ias" the test result for a dry bond. Shear stress testswere also performed on other veneer bonds similarly prepared from theresins of Examples I and II, after the bonds had been water-soaked atroom temperature for 48 hours and after 11 they had been immersed inboiling water for 4 hours. The results of the lap shear stress tests aregiven in Table I.

Values in parentheses indicate the percent of wood failure in each shearstress test.

From the data of Table I, it can be seen that, on being thermoset, theresorcinol-containing resins produced in the first runs of Examples Iand II provided bonds having good shear strength and high resistance toloss of shear strength from the action of water on the bonds, and thatthe shear strength properties of the resorcinol-containing bonds were ingeneral substantially equivalent to those of bonds provided by resinsproduced in the second runs of the corresponding examples and containingno resorcinol.

Although the present invention has been described with preferredembodiments, resort to modifications and variations can be had withoutdeparting from the spirit and scope of the invention, as those skilledin the art will readily appreciate. Such variations and modificationsare therefore considered to be within the purview and scope of theappended claims.

What is claimed is:

1. A process for producing a thermosettable watersoluble resin useful asa binder for bonded products made from fibers, particles, or sheets,which bonded products possess properties of high bond strength and areresistant against weakening of the bond from exposure to water, saidprocess comprising simultaneously reacting an aldehyde, a ketone, and atleast two phenolic compounds, said phenolic compounds comprising amonohydric phenol and resorcinol and said resorcinol constitutingbetween one mole percent and 25 mole percent of said phenolic compounds,in molar proportions of between 3 and 6 moles of the. aldehyde per moleof the phenolic compounds and of between 1 and 1.5 moles of the ketoneper mole of the phenolic compounds, in the presence of a base capable ofcatalyzing the condensation reaction of the aldehyde, the ketone, andthe phenolic compounds, at a temperature of between 125 F. and 350 F.,and for a period of time between 30 minutes and 3 hours; said molarproportions being the molar proportions of the aldehyde, the ketone, andthe phenolic compound moieties in the resin product.

2. A process as defined in claim 1, in which the aldehyde isformaldehyde.

3. A process as defined in claim 1, in which the ketone is acetone.

4. A process as defined in claim 1, in which the monohydroxy phenoliccompound is phenol.

5. A thermosettable water-soluble resin produced by simultaneouslyreacting an aldehyde, a ketone, and at least two phenolic compounds,said phenolic compounds comprising a monohydric phenol and resorcinoland said resorcinol constituting between one mole percent and 25 molepercent of said phenolic compounds, in molar proportions of between 3and 6 moles of the aldehyde per mole of the phenolic compounds and ofbetween 1 and 1.5 moles of the ketone per mole of the phenoliccompounds, in the presence of a base capable of catalyzing thecondensation reaction of the aldehyde, the ketone,:ind the phenoliccompounds, at a temperature of between 125 F. and 350' F., and for aperiod of time between 30 minutes and 3 hours; said molar proportionsbeing the molar proportions of the aldehyde, the ketone, and thephenolic compound moieties in the resin product.

6. A resin as defined in claim 5, in which the aldehyde is formaldehyde.

7. A resin as defined in claim 5, in which the ketone is acetone.

8. A resin as defined in claim 5, in which the mono- WILLIAM H. SHORT,Primary Examiner.

H. SCHAIN, Assistant Examiner.

